A known hydraulic fluid control valve for a power steering gear includes a valve core rotatable within a valve sleeve. The core and the sleeve control the pressure of hydraulic fluid flowing through the valve between a pump, a reservoir, and a pair of opposed fluid chambers in a hydraulic motor. When the core and the sleeve are in centered positions, the hydraulic fluid pressures in the opposed fluid chambers are equal. When the core and the sleeve are rotated from the centered positions, a plurality of lands and grooves on the core and the sleeve cooperate to increase the hydraulic fluid pressure in one of the opposed fluid chambers, and thereby to provide hydraulic power steering assist in the steering gear.
Such a valve may also include a centering mechanism. The centering mechanism resists rotation of the core and the sleeve from their centered positions, and urges them to return to their centered positions.